pyiceberg-core: create even smaller artifacts

[kevinjqliu]

Which issue does this PR close?

• Closes investigate pyiceberg-core size (currently ~100mb) #1839

What changes are included in this PR?

use lto = "thin", opt-level = "z"

Tested building the wheel locally on mac. And this is the winning combination.

Change	Wheel Size	Build Time	Notes
fat LTO, opt-level=3 (default)	21 MB	~3 min	Original
fat LTO, opt-level=z	12 MB	~3 min	43% smaller
thin LTO, opt-level=z	12 MB	~1.5 min	Same size, 2x faster build!
no LTO, opt-level=z	13 MB	~1 min	Slightly bigger

Size Reduction

This branch vs main branch w/ #1841

Name	Old Size	New Size	% Decrease
wheels-macos-latest-universal2-apple-darwin	44.4 MB	23.5 MB	47.07%
wheels-ubuntu-latest-aarch64	66.1 MB	40.9 MB	38.12%
wheels-ubuntu-latest-armv7l	70.5 MB	33.1 MB	53.05%
wheels-ubuntu-latest-x86_64	23.8 MB	13 MB	45.38%
wheels-windows-latest	25.9 MB	12.7 MB	45.38%
wheels-sdist	575 KB	574 KB

Are these changes tested?

Yes
https://github.com/apache/iceberg-rust/actions/runs/19285828822

[liurenjie1024]

Thanks @kevinjqliu for this fix!